U.S. patent application number 15/836053 was filed with the patent office on 2018-08-02 for acoustic apparatus.
This patent application is currently assigned to ALPINE ELECTRONICS, INC.. The applicant listed for this patent is ALPINE ELECTRONICS, INC.. Invention is credited to Kei Tanabe.
Application Number | 20180220227 15/836053 |
Document ID | / |
Family ID | 60673607 |
Filed Date | 2018-08-02 |
United States Patent
Application |
20180220227 |
Kind Code |
A1 |
Tanabe; Kei |
August 2, 2018 |
ACOUSTIC APPARATUS
Abstract
An acoustic apparatus may include a frame having an annular open
portion that opens in an axial direction; a diaphragm supported by
being attached to the annular open portion via a flexible edge
member so as to be capable of vibrating in the axial direction; and
a driving unit connected to the diaphragm at a center portion of
the diaphragm, where the driving unit is configured to apply a
driving force in the axial direction to the diaphragm. The
diaphragm has a rotationally symmetric shape around an axis of the
diaphragm when viewed in the axial direction. The diaphragm
includes a sheet member having an orientation dispersion structure
in which shape-anisotropic fillers are dispersed in a resin with
long axes of the fillers oriented in one predetermined direction,
and the diaphragm has mechanical characteristics having two-fold
rotation symmetry around the axis.
Inventors: |
Tanabe; Kei; (Fukushima,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ALPINE ELECTRONICS, INC. |
Tokyo |
|
JP |
|
|
Assignee: |
ALPINE ELECTRONICS, INC.
Tokyo
JP
|
Family ID: |
60673607 |
Appl. No.: |
15/836053 |
Filed: |
December 8, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04R 31/003 20130101;
H04R 1/2834 20130101; H04R 7/02 20130101; H04R 7/06 20130101; H04R
1/025 20130101; H04R 9/025 20130101; H04R 2307/029 20130101 |
International
Class: |
H04R 1/28 20060101
H04R001/28; H04R 1/02 20060101 H04R001/02; H04R 9/02 20060101
H04R009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2017 |
JP |
2017-015339 |
Claims
1. An acoustic apparatus comprising: a frame having an annular open
portion that opens in an axial direction; a diaphragm supported by
being attached to the annular open portion via a flexible edge
member so as to be capable of vibrating in the axial direction; and
a driving unit connected to the diaphragm at a center portion of
the diaphragm, where the driving unit is configured to apply a
driving force in the axial direction to the diaphragm, wherein the
diaphragm has a rotationally symmetric shape around an axis of the
diaphragm when viewed in the axial direction, and wherein the
diaphragm includes a sheet member having an orientation dispersion
structure in which shape-anisotropic fillers are dispersed in a
resin with long axes of the fillers oriented in one predetermined
direction, and the diaphragm has mechanical characteristics having
two-fold rotation symmetry around the axis.
2. The acoustic apparatus according to claim 1, wherein the
diaphragm has a continuously rotationally symmetric shape around
the axis of the diaphragm when viewed in the axial direction.
3. The acoustic apparatus according to claim 1, wherein the
diaphragm is formed of one seamless sheet member.
4. The acoustic apparatus according to claim 3, wherein the
diaphragm is a vacuum-formed article or a pressure-formed article
formed of a sheet member in which the fillers are dispersed in a
thermoplastic resin.
5. An acoustic apparatus comprising: a frame having an annular open
portion that opens in an axial direction; a diaphragm supported by
being attached to the annular open portion via a flexible edge
member so as to be capable of vibrating in the axial direction; and
a driving unit connected to the diaphragm at a center portion of
the diaphragm, where the driving unit is configured to apply a
driving force in the axial direction to the diaphragm, wherein the
diaphragm has a rotationally symmetric shape around an axis of the
diaphragm when viewed in the axial direction, wherein the diaphragm
includes one seamless sheet member having an orientation dispersion
structure in which shape-anisotropic fillers are dispersed in a
resin with long axes of the fillers oriented in one predetermined
direction; and wherein the diaphragm includes: a high-rigidity
region in which the orientation direction of the fillers is
parallel to a direction from a center portion to an outer
circumferential portion of the diaphragm and flexural rigidity in
the high-rigidity region is high when it is attempted to bend an
area between the center portion and the outer circumferential
portion of the diaphragm, and a low-rigidity region in which the
orientation direction of the fillers is orthogonal to the direction
from the center portion to the outer circumferential portion of the
diaphragm and flexural rigidity in the low-rigidity region is low
when it is attempted to bend an area between the center portion and
the outer circumferential portion of the diaphragm, where flexural
rigidity is continuously decreased from the high-rigidity region to
the low-rigidity region.
6. The acoustic apparatus according to claim 5, wherein the
diaphragm is a vacuum-formed article or a pressure-formed article
formed of a sheet member in which the fillers are dispersed in a
thermoplastic resin.
Description
RELATED APPLICATIONS
[0001] The present application claims priority to Japanese Patent
Appln. No. 2017-015339, filed Jan. 31, 2017, the entire disclosure
of which is hereby incorporated by reference.
BACKGROUND
1. Field of the Disclosure
[0002] The present disclosure relates to an acoustic apparatus
(speaker) having improved acoustic characteristics, in particular,
improved acoustic characteristics in a high range.
2. Description of the Related Art
[0003] Acoustic apparatuses (speakers) should have the ability to
reproduce original sounds as accurately as possible. To satisfy
this objective, speaker components such as diaphragms have been
improved in various ways.
[0004] For example, Japanese Examined Patent Application
Publication No. 63-59638 discloses a diaphragm in which composite
material sheets of a plurality of composite material sheets are
laminated and integrally joined. Each of the composite material
sheets is formed of reinforcing fibers having a high modulus of
longitudinal elasticity and a matrix material that binds the
fibers. The reinforcing fibers of each composite material sheet are
oriented in a radial direction with respect to a vibration
direction of the diaphragm. In the diaphragm, since the reinforcing
fibers having the high modulus of longitudinal elasticity are
dispersed in the matrix material such as a resin, the density
decreases and the specific modulus of longitudinal elasticity
(modulus of longitudinal elasticity/density) increases, and hence a
diaphragm having frequency characteristics in a wide band may be
obtained.
[0005] With use of a diaphragm such as the one disclosed in
Japanese Examined Patent Application Publication No. 63-59638, good
characteristics as those of a diaphragm using a light metal such as
magnesium can be obtained. However, when such a material with a
large specific modulus of longitudinal elasticity is used, in a
case where the diaphragm has a highly symmetric shape, frequency
characteristics having a sharp resonance peak (a band with a sound
pressure being characteristically higher than the sound pressures
in the other frequency bands) based on an axially symmetric mode in
a high range may appear. A specific example of the shape of a
diaphragm being highly symmetric may be a rotationally symmetric
shape with a small rotation angle. A typical example is a
continuously rotationally symmetric shape around the axis thereof.
The shape can be expressed by a plurality of circles whose central
axes are aligned with one another when viewed in the axial
direction. The rotation angle around the axis becomes infinitely
small, and the shape has continuous rotation symmetry.
[0006] An example of a method of suppressing the sharpening of the
resonance peak in such a high range may be a method of decreasing
the symmetry of the shape when viewed in the axial direction. A
specific example may be an oblique-cone diaphragm or a diaphragm
having a modified sectional shape.
[0007] However, the oblique-cone diaphragm and the diaphragm having
the modified sectional shape have complicated shapes and have
difficulty in manufacturing and assembly. A new resonance mode may
be generated due to the eccentricity or modified sectional shape.
When the frequency dependency of the sound pressure is measured, a
spectrum having a characteristic peak or dip (a band in which the
sound pressure is characteristically lower than the sound pressures
in the other frequency bands) may be obtained.
SUMMARY
[0008] Regarding such circumstances in the related art, it is an
object of the present disclosure to provide an acoustic apparatus
in which sharpening of a resonance peak in a high range is properly
suppressed and which has good acoustic characteristics.
[0009] In one aspect of the present disclosure, an acoustic
apparatus (speaker) is provided that addresses the above-described
problems. The acoustic apparatus may include a frame having an
annular open portion that opens in an axial direction; a diaphragm
supported by being attached to the annular open portion via a
flexible edge member so as to be capable of vibrating in the axial
direction; and a driving unit connected to the diaphragm at a
center portion of the diaphragm, and configured to apply a driving
force in the axial direction to the diaphragm. The diaphragm has a
rotationally symmetric shape around an axis of the diaphragm when
viewed in the axial direction. The diaphragm includes a sheet
member having an orientation dispersion structure in which
shape-anisotropic fillers are dispersed in a resin with long axes
of the fillers oriented in one predetermined direction, and the
diaphragm has mechanical characteristics having plane symmetry with
respect to a plane, as a symmetry plane, including the orientation
direction of the fillers and the axis.
[0010] As described above, regarding the oblique-cone diaphragm or
the diaphragm having the modified sectional shape, the shape of the
diaphragm is partly changed from a typical shape (for specific
example, a shape having continuous rotation symmetry around the
axis), and the symmetry of the shape when viewed in the axial
direction is decreased. Hence, sharpening of a resonance peak with
high frequencies is suppressed. By partly changing the shape of the
diaphragm, the shape of the diaphragm may have a partial variation
around the axis. When a driving unit applies an external force to
the diaphragm having such a shape, deformation of the diaphragm
caused by the external force may also vary in accordance with the
variation in the shape of the diaphragm. As a result, when the
diaphragm is vibrated by the driving unit, the symmetry of the
vibration generated at the diaphragm may be decreased and the
resonant frequency may be dispersed. The resonance frequency is
properly dispersed, and hence appearance of a sharp resonance peak
is suppressed.
[0011] The diaphragm of the speaker according to the aspect of the
present invention decreases the symmetry of vibration of the
diaphragm by giving anisotropy to the mechanical strength of a
member forming the diaphragm, without decreasing the symmetry of
the shape of the diaphragm. Specifically, since the sheet member
forming the diaphragm has the orientation dispersion structure, and
the mechanical characteristics in the orientation direction differ
from the mechanical characteristics in the direction orthogonal to
the orientation direction, the mechanical characteristics have
two-fold rotation symmetry with a rotation angle of 180 degrees
around the axis. Hence, the resonance frequency can be efficiently
dispersed without decreasing the symmetry of the shape of the
diaphragm. Owing to this, with forms of the speaker according to
the aspect of the present disclosure, appearance of a sharp
resonance peak is efficiently suppressed.
[0012] In forms of the above-described acoustic device (speaker),
the diaphragm may include one seamless sheet member. The diaphragm
may include a high-rigidity region and a low-rididity region. In
the high rigidity region, an orientation direction of the fillers
is parallel to a direction from a center portion to an outer
circumferential portion of the diaphragm and flexural rigidity is
high when it is attempted to bend an area between the center
portion and the outer circumferential portion of the diaphragm. In
the low-rigidity region, an orientation direction of the fillers is
orthogonal to the direction from the center portion to the outer
circumferential portion of the diaphragm and flexural rigidity is
low when it is attempted to bend an area between the center portion
and the outer circumferential portion of the diaphragm. The
flexural rigidity may be continuously decreased from the
high-rigidity region to the low-rigidity region.
[0013] In some implementations, the diaphragm may have a
continuously rotationally symmetric shape around the axis of the
diaphragm when viewed in the axial direction. As described above,
the shape having the continuous rotation symmetry around the axis
can be expressed by a plurality of circles whose central axes are
aligned with one another when viewed in the axial direction. The
diaphragm having such a shape typically has isotropic mechanical
characteristics around the axis, and hence a resonance peak may be
likely sharpened. However, as described above, in the diaphragm of
the speaker in forms of the present disclosure, the sheet member
forming the speaker has the orientation dispersion structure, and
hence the mechanical characteristics have two-fold rotation
symmetry with a rotation angle of 180 degrees around the axis.
Accordingly, even when the shape of the diaphragm is a highly
symmetric shape around the axis, a sharp resonance peak rarely
appears when the diaphragm is vibrated in the axial direction.
Moreover, the diaphragm with the highly symmetric shape is easily
manufactured, and a peak or a dip due to the shape rarely appears
in the frequency characteristics of the sound pressure, as compared
with the oblique-cone diaphragm or the diaphragm with the modified
sectional shape.
[0014] In some implementations, the diaphragm may be formed of one
seamless sheet member. With the one seamless sheet member, the
acoustic characteristics can be increased without a special
treatment.
[0015] In some implementations, the diaphragm may be preferably a
vacuum-formed article or a pressure-formed article formed of a
sheet member in which the fillers are dispersed in a thermoplastic
resin. The thermoplastic resin is easily handled, and when the
thermoplastic resin is heated, vacuum forming or pressure forming
can be carried out. The vacuum forming and pressure forming can
decrease the cost of the mold as compared with injection molding
etc., and the manufacturing cost may be suppressed.
[0016] In forms of the acoustic apparatus, by giving anisotropy to
the mechanical characteristics using the member having the
orientation dispersion structure as the sheet member forming the
diaphragm, sharpening of a resonance peak in the high range can be
properly suppressed, and good acoustic characteristics can be
obtained. In addition, by increasing the symmetry of the shape of
the diaphragm like a typical diaphragm, a defect caused by the low
symmetry of the shape (appearance of a peak or a dip in the
frequency characteristics of the sound pressure) rarely occurs.
Accordingly, an acoustic apparatus including a diaphragm with a
shape that can be easily manufactured, and having good acoustic
characteristics can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1A is a conceptual sectional view illustrating a
structure of a speaker according to one embodiment of the present
disclosure;
[0018] FIG. 1B is a partial plan view in the X1-X2 direction
illustrating a structure of a diaphragm included in the
speaker;
[0019] FIG. 2A is a sectional perspective view illustrating the
structure of the diaphragm of the speaker according to the
embodiment;
[0020] FIG. 2B is a plan view in the X1-X2 direction illustrating
the structure of the diaphragm of the speaker according to one
embodiment; and
[0021] FIG. 3 is a graph showing frequency characteristics of a
speaker according to a modification of one embodiment of the
present disclosure, together with frequency characteristics of
speakers having other structures.
DETAILED DESCRIPTION OF THE DRAWINGS
[0022] Embodiments and implementations of the present disclosure
will be described below with reference to the drawings. FIG. 1A is
a conceptual sectional view illustrating a structure of a speaker
according to one embodiment of the present disclosure, and FIG. 1B
is a partial plan view in the X1-X2 direction illustrating a
structure of a diaphragm included in the speaker. In the plan view,
a shape appearing on the Y1 side in the Y1-Y2 direction is the same
as that appearing on the Y2 side in the Y1-Y2 direction; thus, the
plan view illustrates only the Y2 side. FIG. 2A is a sectional
perspective view illustrating the structure of the diaphragm of the
speaker according to the embodiment, and FIG. 2B is a plan view in
the X1-X2 direction illustrating the structure of the diaphragm of
the speaker according to the embodiment. The sectional perspective
view illustrates a section in which a sectional area of the
diaphragm of the speaker is the maximum.
[0023] As illustrated in FIG. 1A, a speaker 1 may include a frame
11 having a substantially truncated cone shape and various members
attached to the frame 11. The frame 11 includes, at an outer
circumferential edge thereof, an annular open portion 11a having a
circular-ring shape and a spoke-like support 11c extending from the
annular open portion 11a. In the drawing, the support 11c is
indicated by a discontinuous line having cut-out holes 11b for
convenience of understanding.
[0024] A diaphragm 12 that generates a sound pressure in the
speaker 1 includes a flexible edge member 12a at an outer
circumferential edge of the diaphragm 12. The diaphragm 12 is
supported by being attached to the annular open portion 11a via the
flexible edge member 12a so as to be capable of vibrating in the
axial direction (X1-X2 direction in FIG. 1A).
[0025] The diaphragm 12 has a substantially truncated cone shape
and has a circular outer shape when viewed in the axial direction
(X1-X2 direction). The diaphragm 12 includes the flexible edge
member 12a at the outer circumferential edge thereof and is
attached to the annular open portion 11a of the frame 11 via the
flexible edge member 12a. In the speaker 1 in FIG. 1A,
specifically, the flexible edge member 12a is bonded to the annular
open portion 11a of the frame 11 using an adhesive agent. Supported
by the frame 11 as described above, the diaphragm 12 can vibrate in
the X1-X2 direction. The diaphragm 12 includes an opening
(diaphragm opening) 12b at a center portion when viewed in the
axial direction (X1-X2 direction). The diaphragm 12 is connected to
a bobbin 15 at an inner circumferential surface of the diaphragm
opening 12b. The bobbin 15 is a part of a driving unit (described
later).
[0026] A dust cap 13 having a hemispherical-cap shape is disposed
on the X2 side of the diaphragm 12 in the X1-X2 direction to cover
the diaphragm opening 12b. The dust cap 13 is a member that
suppresses unstable operation of the bobbin 15 because a foreign
substance enters the diaphragm opening 12b toward the X1 side in
the X1-X2 direction.
[0027] The support 11c of the frame 11 has a truncated cone shape
and has a top portion (magnetic circuit mount portion 11d) on which
a magnetic circuit 14 is mounted. The magnetic circuit 14 includes
a columnar center pole 14a. The center pole 14a has a central axis
directed in a vibration direction (axial direction (X1-X2
direction)) of the diaphragm. Around the rear (the X1 side in the
X1-X2 direction) of the center pole 14a, a bottom plate 14b is
disposed so as to be integral with the center pole 14a. On the
front side (the X2 side in the X1-X2 direction) of the bottom plate
14b, an annular magnet 14c is mounted. On the front side (the X2
side in the X1-X2 direction) of the magnet 14c, an annular top
plate 14d is mounted. The provision of the magnet 14c forms an
annular magnetic gap 14e between the center pole 14a and the top
plate 14d. The bottom plate 14b and the top plate 14d form a
yoke.
[0028] On the rear side (the X1 side in the X1-X2 direction) of the
diaphragm 12, the bobbin 15 having a cylindrical shape is secured.
As illustrated in FIG. 1A, the bobbin 15 is inserted into the
magnetic gap 14e of the magnetic circuit 14 positioned on the rear
side (the X1 side in the X1-X2 direction) of the diaphragm 12. The
bobbin 15 includes a portion inserted into the magnetic gap 14e,
the portion having a side surface around which a voice coil 16 is
wound. The bobbin 15 reciprocates in the axial direction (X1-X2
direction) in accordance with a current flowing through the voice
coil 16 positioned inside the magnetic gap 14e, which causes the
diaphragm 12 to vibrate and generate a sound pressure.
[0029] A damper 17 is disposed between the diaphragm 12 and the
magnetic circuit 14 in the axial direction (X1-X2 direction). The
damper 17 is supported by the support 11c of the frame 11 at an
outer circumference side of the damper 17, and supports the bobbin
15 at an inner circumference side of the damper 17. The damper 17,
in addition to the diaphragm 12, also reciprocates in the axial
direction (X1-X2 direction) along with the reciprocation of the
bobbin 15. The damper 17 is formed of an elastic member. In a state
in which no current flows through the voice coil 16, the damper 17
has a function of returning the bobbin 15 to a neutral position by
using an elastic recovery force.
[0030] The speaker 1 having such a structure can generate, as
described above, a sound pressure in the axial direction X1 (X1-X2
direction) by causing a current to flow through the voice coil 16
to thereby cause the diaphragm 12 to vibrate. The proportionality
coefficient between the magnitude of the current flowing through
the voice coil 16 and the magnitude of a sound pressure to be
generated is ideally the same at any frequency. However, in
reality, for example, the resonant frequency of the speaker 1
influences the frequency dependence of the sound pressure to have a
peak (a band in which the sound pressure is high) and a dip (a band
in which the sound pressure is low) in a specific range. In
particular, when the diaphragm 12 has a shape continuously
rotationally symmetric around the axis (the line in the X1-X2
direction) like the speaker 1 illustrated in FIG. 1, that is, when
the diaphragm has a shape which may be expressed with a plurality
of coaxial circles, a resonance peak in a high range is likely
sharpened when viewed in the X1-X2 direction.
[0031] FIG. 3 is a graph showing frequency characteristics of a
speaker according to a modification of one embodiment of the
present disclosure, together with frequency characteristics of
speakers having other structures. The graph indicated by a gray
broken line in FIG. 3 is a graph showing frequency characteristics
of a speaker (hereinafter, referred to as reference speaker)
including a diaphragm having mechanical characteristics isotropic
around the axis (the line in the X1-X2 direction), that is, a
speaker with the shape and mechanical characteristics having
continuous rotation symmetry around the axis (the line in the X1-X2
direction). As illustrated in FIG. 3, there is found a peak at
which the sound pressure is locally high with frequencies around 5
kHz. This peak is based on the resonance of the diaphragm.
[0032] In order to decrease the intensity of such a resonance peak,
the diaphragm 12 of the speaker 1 is formed of a sheet member that
has an orientation dispersion structure in which shape-anisotropic
fillers FB are dispersed in a resin with the long axes thereof
oriented in one predetermined direction (specifically, orientation
direction D1 along the Y1-Y2 direction) as illustrated in FIGS. 2A
and 2B.
[0033] Using the sheet member having the orientation dispersion
structure to form the diaphragm 12, as described above, improves
the mechanical characteristics of the diaphragm when compared with
a case in which the fillers FB are not contained. As a result, the
mechanical characteristics of the diaphragm 12 can be improved.
[0034] Examples of the shape-anisotropic fillers FB include
carbon-based materials, such as carbon fiber and carbon nanotubes,
and oxide-based materials, such as glass fiber. The length of each
of the fillers FB may be any length. Non-limiting examples of the
length are a length between 0.01 to 10 mm inclusive, or may be
preferably a length between 0.1 mm to several millimeters inclusive
from a viewpoint of ease of handling. The ratio of the length of
the major axis of each filler FB to the length of the minor axis of
the filler FB, what is called the aspect ratio, may be any ratio.
The aspect ratio of each filler FB may be preferably 5 or higher.
The type of the resin contained in the sheet member is not limited.
Non-limiting examples of the resin are polyolefin, such as
polyethylene and polypropylene; polyester, such as polyethylene
terephthalate; polyamide, such as nylon 6,6; polyvinyl chloride;
and polyimide.
[0035] The method of manufacturing the sheet member may be any
method, as long as the sheet member can have an appropriate
orientation dispersion structure. Specific examples of the method
of manufacturing the sheet member are extrusion forming, expansion,
and blow forming. The sheet member may preferably contain a filler
having high orientation dispersion properties, so as to have high
in-plane uniformity. In such a case, the sheet member is preferably
an extrusion-formed article. With such a sheet member being the
extrusion-formed article, the uniformity of the material of the
sheet member as a constituent material of the diaphragm 12 is
increased, which may make it easy to realize the speaker 1 having
excellent quality uniformity.
[0036] The diaphragm 12 is formed of such a sheet member. The
manufacturing method of the diaphragm 12 is not particularly
limited. The manufacturing method of the diaphragm is typically
vacuum forming or pressure forming of forming a sheet member with
use of a mold having an exhaust hole. By heating the sheet member
during vacuum forming etc., formability may be increased.
[0037] Since the sheet member has the orientation dispersion
structure as described above, the sheet member has anisotropic
mechanical characteristics. Specifically, the mechanical
characteristics in the orientation direction D1 differ from the
mechanical characteristics in a direction orthogonal to the
orientation direction D1. The modulus of longitudinal elasticity
and specific frequency are typically relatively high in the
orientation direction D1, and the tensile elasticity is relatively
high in the direction orthogonal to the orientation direction
D1.
[0038] As described above, since the sheet member has the
orientation dispersion structure in the diaphragm 12 formed by
including the sheet member, the mechanical characteristics, in
particular, the modulus of longitudinal elasticity of the diaphragm
12 is increased as compared with a diaphragm formed of a sheet
member in which fillers are not dispersed. Also, since the sheet
member has the anisotropic mechanical characteristics, the
mechanical characteristics of the diaphragm 12 in the orientation
direction D1 of the sheet member differ from the mechanical
characteristics of the diaphragm 12 in the direction orthogonal to
the orientation direction D1. As a result, the mechanical
characteristics of the diaphragm 12 have two-fold rotation symmetry
with a rotation angle of 180 degrees around the axis (the line in
the X1-X2 direction). Hence, the shape of the diaphragm 12 of the
speaker 1 has continuous rotation symmetry around the axis (the
line in the X1-X2 direction), and the mechanical characteristics of
the diaphragm 12 have two-fold rotation symmetry. In terms of
rotation symmetry, two-fold rotation symmetry has the lowest
symmetry. Due to this, when the diaphragm 12 vibrates, a resonance
peak in a high range is less likely sharpened in the frequency
characteristics of the sound pressure.
[0039] In other words, the diaphragm 12 includes a high-rigidity
region and a low-rigidity region. In the high-rigidity region, the
orientation direction of the fillers is parallel to a direction
from a center portion to an outer circumferential portion of the
diaphragm 12 and flexural rigidity there is high when it is
attempted to bend an area between the center portion and the outer
circumferential portion of the diaphragm 12. In the low-rigidity
region, the orientation direction of the fillers is orthogonal to
the direction from the center portion to the outer circumferential
portion of the diaphragm 12 and flexural rigidity there is low when
it is attempted to bend an area between the center portion and the
outer circumferential portion of the diaphragm 12. Flexural
rigidity is continuously decreased from the high-rigidity region to
the low-rigidity region. This causes the resonance peak in the high
range to be continuously dispersed.
[0040] FIG. 3 shows the frequency characteristics of the speaker 1
according to an aspect of the present disclosure using a solid
line. As shown in FIG. 3, there is no sharp peak in a band around 5
kHz whereas a peak is clearly found in the graph indicated by the
gray broken line (the frequency characteristics of the reference
speaker).
[0041] FIG. 3 shows the frequency characteristics of a speaker
including an oblique-cone diaphragm (black broken line), and the
frequency characteristics of a speaker including a diaphragm with a
modified sectional shape (black fine dotted line), although the
basic shape of each of the speakers is common to the shape of the
speaker 1. The outer shape of the diaphragm with the modified
sectional shape has, for example, an S-shaped ridge line, the shape
which has eight-fold rotation symmetry around the axis (the line in
X1-X2 direction).
[0042] In the case of the speaker including the oblique-cone
diaphragm, a dip appears with frequencies around 5 kHz. This may be
caused by rolling of the diaphragm having an eccentric shape. In
the case of the speaker including the diaphragm with the modified
sectional shape, a strong peak is found with frequencies around 5
kHz although the intensity thereof is slightly lower than that of
the reference speaker. This may be because the diaphragm still has
a highly symmetric shape around the axis (the line in the X1-X2
direction).
[0043] Illustrative embodiments and implementations of the present
disclosure have been described above. However, the present
disclosure is not limited thereto. For example, a configuration
realized through appropriate addition, omission, and design change
of components by a person skilled in the art with respect to the
aforementioned embodiments or application examples thereof and a
configuration realized through an appropriate combination of the
features in the embodiment are included in the scope of the present
disclosure provided that such speakers realize the concept of the
present invention.
[0044] For example, the diaphragm 12 may be a formed article having
a laminated structure including the sheet member having the
above-described orientation dispersion structure and an exterior
sheet. The provision of the exterior sheet improves the design of
the diaphragm. However, the weight of the diaphragm is increased,
and hence the acoustic characteristics may be decreased (for
example, a sound pressure in a high range may be decreased).
[0045] It is therefore intended that the foregoing detailed
description be regarded as illustrative rather than limiting, and
that it be understood that it is the following claims, including
all equivalents, that are intended to define the spirit and scope
of this disclosure.
* * * * *